Testing incandescent lamps and other evacuated vessels



Nov. 23 1926. 1,607,823

- D. s. GUSTIN TESTING INCANDESCENT LAMPS AND 0mm EVACUATED VESSELSFiled March 1922 INVENTOR DANIEL 5 GUSTIN ATTORNEY Patented Nov. 23,1926..

UNITED STATES PATENT OFFICE.

DANIEL SNYDER GUSTIN, OF NEWARK, NEW JERSEY, ASSIGNOR TO WESTINGHOUSELAMP COMPANY, A CORPORATION OF PENNSYLVANIA.

TESTING INCANDESCENT-LAMPS AND OTHER EVACUATED VESSELS.

Application filed March 29,1922. Serial No. 547,696.

This invention relates to the manufacture of incandescent lamps andother evacuated vessels and more particularly to a method for testingthe degree of vacuum therein.

An object of my invention is to reduce the formation of gases in a lampwhile coiling the same.

Another object is the determination of the degree of exhaust in anincandescent lamp or other evacuated vessel without subjecting v thesame to a discharge of too high power.

A further object is the use of Geissler tubes or the like as indicatorsto show the degree of vacuum in an incandescent lamp during theprocess-of coiling.

The usual method of coiling comprises the subject on of the lamp to ahigh-power discharge from an induction coil. This has proved to bedisadvantageous onaccount of the liberation of undesirable gases duringsuch test, as indicated by a higher residual,

pressure than that of one not so treated. In addition, the discharge. isapt to, and frequently does, actuatethe getter, thereby partiallydestroyin its value. The gas is not only liberated from the walls of thebulb and the filament and other lamp parts but appears to he -liberatedfrom the exhaust connections for the lamp, such as the oiled rubbertubing. The amount of gas evolved during this coiling operation appearsto depend on the strength ofthe current used and the length of time towhich a jected thereto.

By my invention, the degree of exhaust of the lamp is determined, notfrom the appearance of the discharge within the lamp itself, but fromthe appearance of one .or more glass tubes provided with electrodes andfilled with a suitable gas, such as Geissler tubes employed inconnection therewith. A preferred method consists substantially in theuse of two Geissler tubes, one in series with the lamp during thecoiling operation and the other in parallel across the terminals lamp issubof the secondary winding of the induction coil for the purpose ofindicating the desired potential. With this arrangement, the degree ofexhaust in the lamp can be detertherefore, the coil may be so adjustedas to cause a visible discharge through one or both of the Geisslertubes without the lamp showing an appreciable discharge. By this means,the vacuum of the lamp will not be impaired to any extent, .as waspreviously the case when a high-power discharge occurred therethrough.

Other objects and advantages of the invention will be' apparent as thedescription proceeds. i

A preferred embodiment of the invention is illustrated in theaccompanying drawing whichis a diagram showing a lamp connected for testaccording to my invention.-

The invention, as illustrated, is applied to a vacuum lamp, however, thesame method may be employed for testing other evacuated containers.

Referring to the drawing, the lamp 1 is shown connected by its exhausttube 2 to a suitable exhaust system 3. An induction coil 4 has a primarywinding which is connected to a battery 5 or other suitable source ofelectricity and is preferably provided with the usual condenser 6.inshunt with the interrupter 7. As shown, a Geissler tube the leading-inwires 11 of the-lamp. Geissler tube 10 has preferablya lower filling gaspressure than Geissler tube'8 so that the combined resistance of tube 10and the lamp 1 will approximate thatof Geissler tube 8.

In testing 40 watt, 110 volt lamps, satisfactory results have beenobtained by using Geissler tubes approximately 3" long and s f indiameter. Dumet leadin -in wires of the usual construction, with anickeliron core and copper sheath and such as might be made according tothe disclosure in the patent to B. E. Eldred, No. 1,140,134, granted May18, 1915, with nickel extensions were used as electrodes therein. Usingargon as the filling gas, the pressure thereof in tube 8 should be about10 of mercury and that in tube 10 about 5". These same tubes andpressures could probably be used with satisfaction on 25 and watt, 110volt lamps also. For testing 100 watt, 110" volt lamps, the pressure ofthe argon in tube 8 should be increased to approximately 15 of mercury.That is, the larger the bulb of the lamp the higher the pressure orresistance ofthe tube 8 should be, compared with that of tube 10. Thevoltage from the secondary of the induction coil 4 should then becorrespondingly increased to give a visible discharge through the tube 8when either an air lamp or one with a Very good vacuum is tested. Uponclosing the switch 12 the coil is actuated to cause a visible dischargethrough one or both of the Geissler tubes, depending upon the degree ofexhaustion of the lamp being tested.

The operation of this system depends on the resistance offered by thelamp. A very good vacuum offers a fairly high resistance, a reasonablygood vacuum a smaller resist ance, diminishing with'increase of pressureuntil a fairly high critical pressure is reached when the resistancebegins to again increase very rapidly. This permits an easydetermination of the degree of vacuum in the lamp. The system may beadjusted initially by-testing either an air lamp or one with a vacuumknown to be very good so that the tube 8. shows a heavy dischargeand thetube 10 is practically unaffected in appearance.

The experimental results of testing by this method are as follows. Ifthe lamp 1 has a very good vacuum, the tube 8 will show a heavydischarge whereas the tube 10 will only flicker occasionally. If thevacuum in the lamp is fairly good, the tube 8 will remain black and thetube 10 will have a forked discharge. If the vacuum is poor, the tube 8will be black while the tube 10 will show a very heavy discharge. If anair lamp is tested by this method, thetube 8 will show a very. heavydischarge whereas the tube 10 will remain black.

The effect of using a Geissler tube in series with the lamp is shown bythe following table which is taken from an actual test. The lamp wasexhausted to 2.2 microns, the pump pinched off and the lamp coiledbetween the leads and the bulb. The pressure was read at the start andevery two minutes on a McLoed gauge. The first column after the timecolumn shows the normal increase due to leakage of the system. The nexttwo "columns show the'increase when coiling with Mierons coiled no tube.

Microns coiled G. No. 2.

Mierons coiled G. No. 1.

Microns Time min. no con By the use of this methothlittle or no gas isliberated from the walls of the exhaust system while a lamp is beingtested. The method is moro'accurate than that heretofore used becausechanges of the vacuum degree are followed by very definite changes inthe discharge through the Geissler tubes. More careful voltageregulation is possible because of the lower arcing potential of" argonor other inert gas as compared with that of air. Another advantage isthat the (ieissler tube indicators do not need to be near the lamp ontest and may therefore, be placed in the most desirable position forobservation. I

\Vith this system of testing, no ground connections are used and;therefore. undesirable stray currents are cut down. Fluids, such aswater vapor or hydrogen, show up just as definitely as air by the use ofthis method, whereas they do not show up properly under the old method.

By means of the present invention, an evacuated vessel may be tested ina more accurate and more easily observed way than heretofore. Geisslertubes of different sizes or with different-gas pressures therein may beused for lamps of different sizes, thereby giving great flexibility tothis method. Lamps'may be rapidly tested without the former harmfuleffects thereto, because the testing current is much reduced by thismethod.

While I have illustrated what I now consider to be the preferredembodiment of my invention, it is to be understood that many changes maybe effected therein and that the same is to be limited only by the scopeof the appended claims.

What is claimed is 1. The method of determining the degree of exhaust inan evacuated vessel without passing an extensively high currenttherethrough which comprises passing an electrical current through aninert gas in series with the atmosphere within the lamp to give visibleindication by reason of the inert gas of the degree of vacuum in saidlamp.

2. An apparatus for coiling an incandesthe secondary winding of the coiland a second Geissler tube connected in series with the evacuatedportion of the lamp under test.

3. An apparatus for determining the degree of vacuum in an evacuatedcontainer without subjecting it to too high a power discharge comprisingan induction coil, a Geissler tube connected across the secondarywinding'of the same for indicating the potential thereof, and anotherGeissler tube connected to said winding and in series with the evacuatedcontainer for reducing the power impressed on the same.

4. An apparatus for determining the degree of vacuum in an evacuatedvessel including an induction coil, comprising primary and secondarywindings, a Geissler tube having a relatively high gas filling pressureacross the-terminals of the secondary winding, a second Geissler tubehaving a relatively low filling gas pressure connected in series withthe vessel to be tested and connected across the secondary terminals ofthe coil.

5. An apparatus for testing the degree of vacuum in an evacuatedcontainer comprising an induction coil including a primary windingconnected to a suitable source of electricity and a secondary windingconnected to a Geissler tube, containing an inert gas at a pressure lessthan atmospheric, in series with the container.

6. An apparatus for testing the degree of vacuum in an' evacuatedcontainer comprising an induction coil including a primary windingconnected to a suitable source of haust in a container being evacuatedcomprising an induction coil including a secondary winding and a primarywinding suitably connected to a source of electricity, a Geissler tubeconnected thereto to indicate the potential developed in the' secondarywinding and a second Geissler tube also connected to the coil and inseries withthe cons t'ainer.

8. Means for indicating the degree of vacuum in a vessel being exhaustedcomprising an adjustable source of high p0? tential, a tube connectedthereto as an indicator for adjusting the potential and containing asuitable gas at a relatively high pressure and a second tube, of similarconstruction but whose gas pressure is relatively low, connected inseries with the vessel and this series arranged in parallel with thefirst tube.

In testimony whereof, I have hereunto subscribed my name this 28th dayof March, 1922. 1 2

DANIEL SNYDER eus'rnv.

